δ相诱导GH4169合金楔横轧心部缺陷形成机理

Formation mechanism of internal defects in GH4169 alloy induced by δ phase during cross wedge rolling

关键词:  GH4169合金  楔横轧  心部缺陷  δ相  临界半径

Key words:  GH4169 alloy  cross wedge rolling  internal defects  δ phase  critical radius

摘要:

楔横轧工艺中常见的心部缺陷问题限制了该工艺在航空航天领域的发展。针对此问题,以GH4169合金楔横轧件为实验对象,采用OM、SEM对轧件的微观组织进行表征,并在轧制前预析出不同含量的δ相,探讨δ相含量对心部缺陷形成的影响。同时,借助有限元数值模拟软件对楔横轧过程中轧件的金属流动、应力、应变等演化规律进行分析。结果表明:楔横轧成形过程中预析出的短小片层状δ相会发生球化行为,转变成短棒状和颗粒状δ相。其中,完全球化的δ相对轧件心部缺陷无明显影响,而未完全球化的片层状δ相在楔横轧过程中因为轴向拉应力和周向剪切应力的共同作用易成为心部裂纹源,导致轧件心部出现缺陷。此外,在分析金属流动规律时发现,轧件心部的金属在径向有异常流动的趋势,且存在异常流动临界半径。

Abstract:

The common issue of internal defects in cross wedge rolling process limits the development in the field of aerospace. To address this problem, cross wedge rolled GH4169 alloy products were selected as the experimental subjects. The microstructure of cross wedge rolled GH4169 alloy parts was characterized by metallographic microscope and scanning electron microscope. And the effect of δ phase on the formation of internal defect was studied by precipitating different content of δ phase before rolling. At the same time, the evolution laws of metal flow, stress and strain during cross wedge rolling process were analyzed by finite element simulation. The results show that the pre-precipitated plate-like δ phase undergoes spheroidization, transforming into short rod-like and spherical δ phase. The fully spheroidization δ phase has no obvious effect on the internal defects of rolled parts. In contrast, the partially spheroidized layered δ phase is prone to becoming a the internal crack source due to the combined effects of axial tensile stress and circumferential shear stress during the cross wedge rolling processes, resulting in the internal defects. In addition, the analysis of metal flow patterns revealed an anomalous radial flow direction in the internal metal, along with the existence of a critical radius for this abnormal flow.